doc: boards: x86: Correct EFI boot documentation

Use generic note instead of Windows specific one.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>

Author: finikorg

boards/x86/common/efi_boot.rst

@@ -38,8 +38,7 @@ Boot the board to the EFI shell with USB flash drive connected.
    website for more information.
 
    .. note::
-      On Windows, PuTTY has an option to set up configuration for
-      serial data.  Use a baud rate of 115200.
+      Use a baud rate of 115200.
 
 #. Power on the board.